1. Field of the Invention
The present invention relates to moistureproof sealing of a container. More particularly, it relates to shielding from moisture a moisture absorptive or moisture curable composition stored in a container having a lid caulked along its periphery to the mouth of the container.
2. Description of the Prior Art
A container such as, a drum, or a cartridge, has a lid caulked along its periphery to the mouth of the container. By such a caulked structure, the container is sealed more or less and, as such, is used for storing a moisture absorptive material or a moisture curable composition. However, such sealing is not complete in a strict sense, and it frequently occurs that the stored material or composition undergoes a property change upon absorption of moisture coming in through the sealing portion or solidifies to close the mouth portion of the container.
In order to prevent such a problem, it has been common to employ a physical method for the prevention of the moisture, e.g. such that an inert gas such as nitrogen or carbon dioxide gas is filled in the container, or a solid moisture absorber such as quick lime, silica gel or zeolite is used. However, such a physical method has not yet adequately solved the problem. Namely, in the case where an inert gas is filled in the container, the air in the container is simply replaced by the inert gas, and the effect thereby obtainable is the prevention of oxidation rather than the prevention of moisture. Such a method is intended primarily to prevent the oxidation of the stored material and thereby to prevent the polymerization or solidification of the material at room temperature. In the case of the solid moisture absorber, the moisture absorbing effect is obtainable only when the air containing moisture contacts the absorber which is usually contained in an inner receptacle placed in the container, and thus, the absorber does not provide any positive effect to prevent the inflow of the moisture through the sealing portion along the mouth of the container. Further, the moisture absorber loses its moisture absorbing property upon absorption of moisture. Therefore, once the absorber has absorbed moisture to saturation, it no longer serves as a moisture absorber. Thus, its effective life is limited. For these reasons, no adequate moistureproofing effect has been attained by such conventional physical methods.